1. Field of the Invention
The present invention relates to method of supply amount management of a water treating agent to thermal equipment as represented by a boiler or a cooling tower.
2. Description of the Related Art
In thermal equipment such as a boiler or a cooling tower, for preventing water from causing corrosion or scale formation on a heat-transfer surface, water treating agents have generally been added to water to be supplied. In recent years, in the boiler, water treating agents made of food additives containing silica, an alkaline agent, and a scale inhibitor have been used, as described in JP 2003-159597 A. Here, the silica is blended so that it forms a coating on the heat-transfer surface of the boiler to protect the surface from corrosion by water. In addition, the alkaline agent is typically an alkali metal hydroxide, which is blended for adjusting water to a pH range of 11 to 12 to make the heat-transfer surface difficult to be corroded. Further, the scale inhibitor is a chelating agent, which is capable of forming a complex with any of hardness components (calcium and magnesium ions) each of which is a scale-promoting component, a copper ion, a zinc ion, an iron ion, and the like in water to be supplied. The scale inhibitor is blended for preventing the scale formation on the interface between the heat-transfer substance and the water.
The supply amount of a water treating agent is determined so that the concentration of the water treating agent in the thermal equipment is within a given range on the basis of the quality of water to be supplied and the operating conditions of the thermal equipment (i.e., the concentration rate of the water treating agent in the boiler). This kind of setting is generally performed by a maintainer for the thermal equipment. For exerting the effect of the water treating agent at maximum, it is important to keep the concentration of the water treating agent within a predetermined range. The maintainer should readjust the supply amount of a water treating agent when the concentration of the water treating agent is insufficient or overabundant. The maintainer also should inform a user that the concentration of a water treating agent is within a predetermined range to allow the user to recognize the maintenance conditions and running costs of the thermal equipment. For those reasons, the concentration of a water treating agent in the thermal equipment should be clarified to manage the supply amount of the water treating agent.
For clarifying the concentration of a water treating agent, it will require a great deal of time and efforts to individually determine all of components to be supplied in the water treating agent in a quantitative manner. In addition, to determine a specific component to be supplied in the water treating agent in a quantitative manner, for example, in the case of the water treating agent disclosed in JP 2003-159597 A, there is a problem in that the concentration of the component calculated from the supply amount thereof does not correspond to the actual concentration thereof. This is because silica forms a coating on the heat-transfer surface. Further, an alkali metal hydroxide is generated when an alkaline component such as sodium hydrogen carbonate in water to be supplied is thermally decomposed. Therefore, particularly in the boiler, there is also a problem in that the concentration of the component calculated from the supply amount thereof does not correspond to the actual concentration thereof.